Lately, there has been an increased awareness of the need to exercise and also for relaxation. This has lead to that the fitness industry has grown and especially the area of fitness equipment. Also the use of personal trainers is increasing. This is due to the fact that persons often want help and feedback during their training. However, the drawback of using a personal trainer is that it must be planned, i.e. it decreases any spontaneous training or relaxation.
Today there also exist a lot of devices that can give feedback to users that are exercising, such as pulse watches, GPS-watches, foot pods, etc. These devices usually consist of one central unit such as a watch and a measuring unit such as an Electrocardiogram (ECG) sensor or foot pod. Typically, the central unit and the measuring unit or units will communicate with each other by radio frequency (RF). If there is more than one sensor connected to the central unit this is often done in a wireless network. However, in practice, it might be difficult to set up such a network for users if they use a lot of different sensors. In the best cases all devices and sensors are from the same manufacturer and are already set up when the user buys the equipment.
The use of wireless networks, in which the signals propagate externally to the user have at least one drawback. Such a wireless network is usually configured to automatically search and connect to any new device in the range of thereof even if the device belongs to another user. Having wireless networks that use different frequencies sometimes solves this problem. However, if there are many users in a limited space there will certainly be problems with interference. It might also be that one user is able to pick up data from a sensor belonging to another user.
There is also a potential problem with body attenuation if a sensor is placed on the back of the body and it shall communicate with a central unit placed in front of the body. Furthermore, a typical wireless network has high power consumption.
However, even if the above-described devices for giving a user feedback would come without the entire mentioned drawback, it is still a big difference to having a personal trainer. A personal trainer can tell a user if he is performing an exercise with the right movements or with the right speed etc.
Hence, an improved exercise system for giving feedback to a user would be advantageous, and in particular a more power efficient and/or interference free exercise system where eavesdropping is difficult, i.e. privacy of users is protected.